The manufacturing of advanced integrated circuits (IC) typically uses about 350 steps. One fourth of these steps are dedicated to semiconductor wafer surface cleaning to remove any contaminants from the previous steps and/or prepare the surface for the subsequent steps. In this regard, the importance of clean semiconductor wafer surfaces in the fabrication of semiconductor devices or advanced integrated circuits has been recognized since the beginning of the industry. Failing to removes trace impurities, such as sodium ions, metals, and particles, from a semiconductor wafer surface is known to be especially detrimental during high-temperature processing because the impurities tend to spread out and diffuse into the semiconductor wafer, thereby altering the electrical characteristics of the semiconductor devices formed in the wafer. Altering a semiconductor device's electrical characteristics cause the device to fail and, therefore, subtracts from a wafer's yield. The inadequate and/or improper drying of a semiconductor wafer surface is also known to negatively affect a wafer's yield.
During advanced integrated circuit manufacturing, it is difficult or sometimes impossible to measure every production wafer. Instead, monitor wafers are processed at the same time along with the product wafers. These monitor wafers (sometimes called witness, filler, or dummy) provide information on how the batch was processed. If the monitor wafers show good results, then the production wafers are assumed to be good as well. To maximize cost savings these monitor wafers are reclaimed. At the end of the IC manufacturing cycle, these wafers are reconditioned and used again for a new cycle. Wafer surface preparation is therefore important with respect to these reclaimed wafers and has become one of the most critical steps in the manufacturing of semiconductors.
With requirements to make sub-100 nm semiconductor devices, as well as economic and environmental pressures, it is desirable that new cleaning techniques be developed. For example, existing techniques for freeing small particles from the surface of a semiconductor wafer utilize a combination of chemical and mechanical processes. One typical cleaning chemistry used in the art is standard clean 1 (“SC1”), which is a mixture of ammonium hydroxide, hydrogen peroxide, and water. SC1 oxidizes and etches the surface of the wafer.
Numerous techniques have also been established with respect to post chemical mechanical processing (“CMP”) cleaning procedures, which focus mainly in reducing the defects (particles) on the wafer surface. For example, wet cleaning methods include immersion cleaning, spray cleaning, and contact cleaning. Most of the process of record (POR) methods typically use brush scrubbers and are based on an RCA type process. These procedures have proven to be costly and do not necessarily produce the desired wafer surface characteristics. These desirable characteristics include low particles counts, undetectable metals, limited surface roughness, and undetectable organics. Accordingly, in light of these aforementioned drawbacks, there is a need for improved cleaning techniques. Such cleaning techniques should be cost sensitive and provide the lowest cost of ownership. This could include a smaller tool footprint, low chemical consumptions, and reduced or limited environmental, safety and health concerns.